1. Field of the Invention
The present invention relates to a method of connecting a priority call in a wireless communication system and an apparatus for the same, more preferably relates to a method of connecting a priority call in a wireless local loop (WLL) system or a cellular system using code division multiple access (CDMA) and an apparatus for the same.
CDMA has the advantages of a higher efficiency of utilization of frequency compared with the conventional time division multiple access (TDMA) and frequency division multiple access (FDMA). It is a multiple access system essential for the next generation of wireless communication systems where a shortage of frequencies will be a concern. The utilization of CDMA, as described above, has the effects of, of course, enabling effective utilization of the frequency and, also, improving privacy and, further, facilitating hand-off between cells.
2. Description of the Related Art
As will be explained in detail later by using the drawings, in the general sequence of channel assignment, when the total number of calls in a wireless section reaches the total number of channels which can be assigned in that same section and a priority call is generated, an ordinary call currently in progress is compulsorily disconnected and the related channel is handed over to that priority call.
In the above sequence, first, the base station controller side determines if a call is an ordinary call or priority call, then requests channel assignment (resource assignment) to a base station transceiver subsystem. The base station transceiver subsystem notifies the base station controller that it cannot assign a channel since all of its wireless channels are in use. When connecting a priority call on a preferential basis, the base station controller then disconnects a certain call among the ordinary calls in progress. Therefore, the base station controller and the exchange disconnect a call in progress between them and then disconnect the call between the base station transceiver subsystem and base station controller and next between the base station transceiver subsystem and terminal. By doing this, an opening arises in the channels (resources) in the wireless section which had previously been all in use, so the base station controller sends the base station transceiver subsystem a channel (resource) assignment request again and the base station transceiver subsystem sends the base station controller a channel (resource) assignment response.
Summarizing the problems to be solved by the invention, as mentioned above, there was the first problem that, in the past, another terminal had to be forcibly disconnected in order to enable a priority call to be preferentially connected, so the quality of service was poor.
Further, there was the second problem that no consideration was given to making full and effective utilization of the resources possessed by the system for improvement of the quality of service.
An object of the present invention is to provide a method of connecting a priority call in a wireless communication system which provides a scheme of channel assignment enabling full and effective utilization of resources of the system and which enables prevention of failure of connection (call loss) of a priority call without compulsorily disconnecting any ordinary calls in progress and an apparatus for achieving that method.
To attain the above object, the method of the present invention sets a maximum threshold Th.III between a critical threshold Th.IV constituting an upper limit, in terms of hardware, on the number of calls able to be assigned channels in a wireless section, and a design threshold Th.II constituting an upper limit in terms of software design. It assigns a priority call a channel and connects the call to the exchange side even if the total number of calls exceeds the design threshold Th.II, but if it determines that the number is smaller than the maximum threshold. Th.III. Further it performs breathing when the total number of calls exceeds the design threshold Th.II, and sends a standby instruction message to the terminal when it determines that the total number of calls has exceeded the maximum threshold Th.III.
Therefore, the wireless communication system assigns channels making full utilization of the resources and prevents failure of connection (call loss) of an emergency call or other priority call.